- Volume 134, Issue 11, 1988
Volume 134, Issue 11, 1988
- Physiology And Growth
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Osmotic Adjustment and the Accumulation of Organic Solutes in Whole Cells and Protoplasts of Saccharomyces cerevisiae
More LessIn the presence of a suitable carbon source, whole cells and protoplasts of Saccharomyces cerevisiae synthesized glycerol as a compatible organic solute in response to increased external osmotic pressure. Boyle-van’t Hoff plots showed that protoplasts, and non-turgid cells, exhibited a linear relationship between volume and the external osmotic pressure (i.e. they behaved as near-ideal osmometers), and that both protoplasts and cells have a component which is not osmotically responsive - the non-osmotic volume (NOV). Glycerol levels in whole cells and protoplasts were elevated by increased external osmotic pressure over a similar time-scale to the period of exponential cell growth, reaching a maximum value at 6–12 h and declining thereafter. This suggests that the restoration of turgor pressure in whole cells was not the sole regulator of glycerol accumulation. Stationary phase whole cells had negligible levels of intracellular glycerol after growth in a medium of raised osmotic pressure. However, intracellular trehalose synthesis in these cells began earlier and reached a higher maximum level than in basal medium. Once exponential growth had stopped, cell turgor and internal osmotic pressure decreased somewhat. These new, lower values may be determined by the extent of trehalose accumulation in stationary phase cells.
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Growth of Yeast Colonies on Solid Media
More LessColonies on nutrient agar of the aerobic yeast Candida utilis show linear increases in diameter and height with time throughout most of the growth cycle. The concentration of glucose in the agar has a negligible effect on radial growth rate although an increase in the glucose concentration prolongs the linear radial growth phase. The rate of increase in height of the colony is proportional to the square root of the initial glucose concentration. A new model that considers both glucose diffusion and oxygen diffusion in the colony is consistent with the observed colony profiles.
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Effects of Ca2+ and a Protonophore on Growth of an Escherichia coli L-Form
More LessThe influence of Ca2+ ions on the growth of an l-form (NC7) derived from Escherichia coli K12 was investigated. In a medium containing NaCl as osmotic stabilizer 1 mm-Ca2+ was required for optimal growth of the l-form, while with KCl as osmotic stabilizer, in a medium containing 0·1 or 1·0 mm-Ca2+, optimium growth was observed at 32 and 37°C, respectively. When the l-form, growing exponentially at 32 C in medium containing KCl and 0·1 mm-Ca2+, was shifted to 37 C growth was strikingly suppressed. In contrast, the suppression of growth in the presence of 1·0 mm-Ca2+ at 32°C was relieved when the culture was shifted to 37°C. When the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP), at a final concentration of 10 m, was added to a medium containing NaCl and sucrose as osmotic stabilizers, together with 10 mm-glucose, the parent strain could grow exponentially. In contrast, growth of the l-form was completely stopped by 10 m-CCCP under the same conditions. In the presence of 20 m-CCCP, the l-form accumulated more than twice as much 45Ca as in the absence of the protonophore. Thus, it is suggested that growth of the l-form NC7 is coupled to the protonmotive force. Possible mechanisms for the coupling of calcium to growth of the l-form are discussed.
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- Systematics
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A Frequency Matrix for Probabilistic Identification of Some Bacilli
More LessA matrix comprising frequencies for positive results for 44 Bacillus taxa for 30 characters has been constructed. The 44 taxa include most of the common species and several clusters of environmental isolates including those described as B.firmus-B. lentus intermediates. The tests, which were chosen for their high diagnostic value, included some of the traditional tests used for identification of bacilli supplemented with a range of sugar fermentations and other characterization tests. The matrix was evaluated by identifying hypothetical median organisms, cluster representatives and a panel of 23 reference strains. All reference strains achieved Willcox probabilities above 0·995. Fifty-eight environmental isolates were also subjected to the 30 tests and identification was attempted. Forty-one strains (70%) achieved a Willcox probability > 0·95, which was considered an acceptable identification, and were assigned to 12 taxa. If the se of taxonomic distance was also considered in the identification score (an acceptable value being < 7·0), the number of acceptable identifications was reduced to 34 (59%). It was encouraging that bacteria from garden soils identified to the common species such as B. subtilis, B. cereus and B. licheniformis whereas some of the bacteria from an estuarine habitat were identified as species such as B. firmus which are normally identified with that habitat.
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Genetic Analysis of Plant Pathogenic Bacteria in the Genus Clavibacter Using Allozyme Electrophoresis
More LessAllozyme electrophoresis was used to examine the relationships among species of Clavibacter, a genus of bacteria mostly causing gummosis in various graminaceous hosts. Allelic profiles were determined at 20 enzyme loci for 28 strains representing C. iranicum, C. rathayi, C. tritici, three subspecies of C. michiganense, Clavibacter sp. from Lolium rigidum, and ‘Corynebacterium agropyri’. The genetic differences between species were at least 70% and between strains within a species up to 35% except for the subspecies of C. michiganense, which differed by up to 75%. The implications of these results for the classification of these Clavibacter spp. is discussed.
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